src/jdk.internal.vm.compiler/share/classes/org.graalvm.compiler.api.directives.test/src/org/graalvm/compiler/api/directives/test/ProbabilityDirectiveTest.java

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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
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 * 2 along with this work; if not, write to the Free Software Foundation,
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package org.graalvm.compiler.api.directives.test;

import org.graalvm.compiler.api.directives.GraalDirectives;
import org.graalvm.compiler.core.test.GraalCompilerTest;
import org.graalvm.compiler.graph.iterators.NodeIterable;
import org.graalvm.compiler.nodes.AbstractBeginNode;
import org.graalvm.compiler.nodes.IfNode;
import org.graalvm.compiler.nodes.ReturnNode;
import org.graalvm.compiler.nodes.StructuredGraph;
import org.graalvm.compiler.nodes.debug.ControlFlowAnchorNode;
import org.junit.Assert;
import org.junit.Test;

public class ProbabilityDirectiveTest extends GraalCompilerTest {

    public static int branchProbabilitySnippet(int arg) {
        if (GraalDirectives.injectBranchProbability(0.125, arg > 0)) {
            GraalDirectives.controlFlowAnchor(); // prevent removal of the if
            return 1;
        } else {
            GraalDirectives.controlFlowAnchor(); // prevent removal of the if
            return 2;
        }
    }

    @Test
    public void testBranchProbability() {
        test("branchProbabilitySnippet", 5);
    }

    public static int branchProbabilitySnippet2(int arg) {
        if (!GraalDirectives.injectBranchProbability(0.125, arg <= 0)) {
            GraalDirectives.controlFlowAnchor(); // prevent removal of the if
            return 2;
        } else {
            GraalDirectives.controlFlowAnchor(); // prevent removal of the if
            return 1;
        }
    }

    @Test
    public void testBranchProbability2() {
        test("branchProbabilitySnippet2", 5);
    }

    @Override
    protected boolean checkLowTierGraph(StructuredGraph graph) {
        NodeIterable<IfNode> ifNodes = graph.getNodes(IfNode.TYPE);
        Assert.assertEquals("IfNode count", 1, ifNodes.count());

        IfNode ifNode = ifNodes.first();
        AbstractBeginNode oneSuccessor;
        if (returnValue(ifNode.trueSuccessor()) == 1) {
            oneSuccessor = ifNode.trueSuccessor();
        } else {
            assert returnValue(ifNode.falseSuccessor()) == 1;
            oneSuccessor = ifNode.falseSuccessor();
        }
        Assert.assertEquals("branch probability of " + ifNode, 0.125, ifNode.probability(oneSuccessor), 0);

        return true;
    }

    private static int returnValue(AbstractBeginNode b) {
        ControlFlowAnchorNode anchor = (ControlFlowAnchorNode) b.next();
        ReturnNode returnNode = (ReturnNode) anchor.next();
        return returnNode.result().asJavaConstant().asInt();
    }
}